Not only was he the first discoverer of the rotifers, but he showed "how wonderfully nature has provided for the preservation of their species," by their tolerance of the drying-up of the water they inhabit, and the resistance afforded to the evaporation of the fluids of their bodies by the impermeability of the casing in which they then become enclosed.
- Diagrammatic Views of Disks of Rotifers: cingulum continuous; trochus dotted; groove shaded; mouth black.
In most rotifers, on the contrary, the trochus is stronger than the cingulum, often lobed, and with some of its cilia aggregated into vibratile styles homologous with the combplates of Ctenophora (q.v.) and the membranelles of ciliate Infusoria (q.v.).
The whole ovary is unilateral and unpaired in most rotifers; symmetrical in Asplanchnaceae, Philodinaceae and Seisonaceae.
The males of rotifers are of relatively rare occurrence, except in the genus A splanchna, where they were first recognized as such by Brightwell in 1841; though those of Hydatina had long since been seen and described as a distinct genus.